properties of nodes:
	Xpos, Ypos: (words) fine X and Y offsets relative to the top left of the airport
	flags: (byte)
		- is it a terminal? (entering it can trigger load/unload phase)
		- is it a hangar?
		- force direction after entering? (if set, next 3 bits contain direction)

size: 5 bytes

properties of edges:
	start, end: (bytes) source and destination node indexes
	special action: (byte)
		0: no special action
		1: helicopter taking off (start and end node must have the same coordinates)
		2: helicopter landing (start and end node must have the same coordinates)
		3: plane landing
		4: plane slowing down to taxi speed
		5: plane speeding up to flight speed
		6: plane taking off
		-- other values are reserved --
	flags: (byte)
		- use full speed, do not taxi
		- no sharp turning
		- if set, helicopters can use this edge
		- if set, normal planes can use this edge
		- the edge can be used when the aircraft is heading for a terminal of the airport
		- ...the hangar of the airport
		- ...the hangar or terminal of another airport
	and_mask: (quadword) the edge can be used only if all of these edges is free
	or_mask: (quadword) the edge can be used if any of these edges is free

size: 20 bytes